Gains in Thermoelectric Performance for Bulk Semiconductor Material

"Researchers from Boston College, MIT, Clemson University and the University of Virginia have used nanotechnology to achieve a 60-90 percent increase in the thermoelectric figure of merit of p-type half-Heusler, a common bulk semiconductor compound. "

This is an example of one approach to improve thermoelectric materials by decreasing the thermal conductivity, while keeping the electrical conductivity relatively unchanged. Usually, the thermopower is also relatively constant, but in this instance the Seebeck coefficient increased. This suggest that grain boundaries may be trapping electrons, leading to increased holes in the sample and energy filtering effect. This may also be due to the involuntary introduction of dopants!

The measurement were done using standard commercial equipments and the uncertainties (without justification) were around 11% for ZT.

An other case for measurement of these quantities at the nanoscale and with reduced uncertainties!

Not that the grain size of the hot-pressed sample is around 200 nm compare to 5-10 nm for the precursors. "Preserving the size of the precursors remains an issue"

The paper can be found here: http://pubs.acs.org/doi/pdfplus/10.1021/nl104138t